1. Field of the Invention
This invention broadly relates to a method of and an apparatus for measuring a surface contour of a measuring object by relatively moving a detector and the object and, more particularly, a method and an apparatus to be used to grasp an outline of the measuring object by relatively moving the detector, such as a non-contacting or contacting type detector, and the measuring object to measure the surface contour of the measuring object with or without keeping a contacting state therebetween, when measuring a right-angled, round-shaped, elliptical profile or a profile combining them all together.
2. Description of the Related Art
An instrument as diagrammatically depicted in FIG. 14 has previously been used to measure a surface contour of an object to be measured. Reference numeral 1 in the drawing is a base for supporting a vertical column 2 thereon. The column 2 has slidably guided, thereon an elevation device 3 movable in an up-and-down direction (Z-direction) by means of a not-shown feed screw. The elevation device 3 has therein a pivotal movement system 4 pivotal by a certain angle (.theta.) about an axis extending perpendicularly to the vertical axis of the column 2 (an axis intersecting the drawing depicted in FIG. 14. The pivotal movement system 4 has a feed screw 6 adapted to be rotated by a motor 5A or a manually operated handle 5B.
The feed screw 6 is provided via a connection member 7 such as a nut to reciprocally carry a detector 8 in a right-and-left direction (X-direction) in the drawing. The detector 8 has a measuring arm 10 with a stylus 9 at the forward end in a state to move up-and-down pivotally and a displacement value detecting sensor (not-shown) such as a liner voltage differential transformer (LVDT) to electrically detect a pivoting degree of the measuring arm 10. Incidentally, a member designated by the reference numeral 2A is a manually operated handle designed to effect a movement of the elevation device 3 vertically up-and-down (Z-direction).
When conducting a measurement with this measuring apparatus, the measuring object W is first located on the base 1 and the stylus 9 is then moved to a point on the upper surface of the measuring object W where the measurement begins. The detector 8 is moved reciprocally in the X-direction corresponding to the rotation of the feed screw 6 by the motor 5A. As the detector 8 moves into the X-direction, the stylus 9 of the measuring arm 10 tosses in response to the surface irregularities of the measuring object W. The movement of the measuring arm 10 is detected by the displacement value detecting sensor (not-shown) to measure the surface contour of the measuring object W.
As can be understood from the above-descriptions, the conventional surface contour measuring apparatus is naturally adapted to regard the rectangular coordinates defined by the base 1 and the column 2 as measurement-datum, so that the mechanical accuracy of the apparatus is always a main factor of accuracy in measurement. The flatness of the base 1, the straightness of the movement of the detector 8 with the measuring arm 10 and the displacement value detecting sensor, and the verticalness of the column 2 against the base 1 should be a main factor of accuracy in measurement. Accordingly, the conventional machine requires a high order of accuracy in assembling and adjusting it and also a great deal of time in maintenance.
When a contacting detector will be used, a stylus thereof may cause the same problem because the radius of the stylus may involve an error, so that some compensation means for the radius error is inevitably to be provided. The error of the radius should influence unnecessarily a measurement signal referencing the Z-direction or the X-direction. This will be remarkable when requiring a high order of accuracy. It is known that, in the non-contacting type detector, an optical axis of the detector should be aligned with a normal axis of the surface of the measuring object as much as possible to achieve the high order of accuracy. However, the conventional apparatus could not shift its posture preferably corresponding to the irregularities of the measuring object to execute a preferable measurement.
The possible measuring range along the X-direction coordinate axis can be extended whereas that of the Z-direction coordinate axis will be limited. Accordingly, the measuring object was limited to be a flat one, so that other ones having a right-angled, round-shaped, elliptical profile or a profile combining them all together could not be measured easily.
If it will be required to conduct the surface contour measurement with the conventional apparatus, the measuring object is generally tilted before measurement. But, the measuring range tends to be narrow in spite of having enough measuring range in the X-direction.
In a circularity test, the measuring object is rotated through measurement while maintaining a coaxial alignment of the measuring object and the rotation device to rotate the measuring object. This alignment work is a time-consuming one and requires much skill. In this measurement, the measuring range or capacity is also limited as in the method which is done by tilting the measuring object. Accordingly, if we need to measure a surface contour of the measuring object, such conventional apparatus was not available to obtain the necessary data.
The object of the present invention is to solve such problems without requiring a precise mechanical processing and adjustment to conduct precise surface contour measurement to thereby provide a method and an apparatus capable of measuring any measuring surface which was not measured by the conventional apparatus.